Problems and solutions for graphite electrodes in EDM function

In EDM process, the appearance of concentrated electric arc of discharge due to inappropriate EDM parameter selection, or bad processing chip discharge, It often comes with scarce electric sparks are and red sparks, and the electric discharge sounds becomes irregular, then produce the so-called unstable discharge. Processing is not stable,then the processing current is not in accordance with the setting, the working current becomes smaller, Various  processing defects will appear in the processing, resulting in waste.
There are often the following abnormal discharge conditions.
(1) Discharge is not stable at the beginning of processing
At the beginning of the graphite electrode working, chip cutting and burr on the workpieces, resulting in concentrated discharge; and due to the huge discharge energy (high peak current, wide pulse width), and pulse interval is too narrow, jet pressure is too large, resulting in discharge instability at the beginning of processing. Therefore, remove the cutting chip, burr attached to the workpiece completely before processing, and remove oxide film, paint, rust during the heat treatment, The current can be set at a smaller value at the beginning, then increase it to the peak current gradually, and set the jet pressure smaller.
(2) producing a granular protrusion
the processing depth is too deep to generate arc, forming a granular protrusion on the workpiece, and the workpiece is discarded
Cause:
Too large pluse width set lead to granular protuberance generated at the angle of the edge of the electrode, thus causing short circuit, causing arcing; electric corrosion product processing chip too much, can’t be drained in time; Wrong processing liquid nozzle angle setting, the machining fluid can not be fully spray into the gap, electric corrosion product processing chip can not be fully drained; Too deep processing depth, processing chips can not be fully drained, stranding at the bottom.
Solution:
Shorten the pulse width ton, longer pulse interval toff, inhibit the production of granular protrusion on the generation and electric corrosion product processing chip; Set the nozzle on the side of the electrode as far as possible; Improve the electrode vibrations times and accelerate the speed of vibration when the processing depth is too deep.
(3) Depression on working ground
In EDM process,when the pulse interval is too small, the electrode vibration speed is slow, jet pressure is weak, resulting in processing chips produced in electric corrosion can not be fully drained and much electric corrosion product bonded on the electrode surface, forming carbon blocks that detach easily in the electrode motion,leading to depression in processing ground.
Solution:
Extends the pulse interval, improves the electrode vibration velocity,and increases jet pressure, also we can suspend the processing, cleaning electrode surface and processing chip on the bottom surface with a brush.
(4) Large gap at entrance
Because of the graphite electrode lifting speed is too slow, processing time is too long at the lower end,then the loss is considerable absolute. and electric corrosion product exist at the discharge gap of the electrode entrance, resulting in "secondary discharge"  (unnecessary discharge due to the involvement of electrical corrosion products on machined surface), discharge gap will expand, processing angle will appear in the depth direction, entrance space will expand. Therefore, in the process of machining, the speed of the graphite electrode can not be too slow.
(5) the processing bottom surface bending or the bottom roughness is not uniform
Due to the pulse interval is too small, especially jet pressure uneven, inter electrode gap is too small, electrical corrosion products can not be fully drained, and the machining surface at the bottom is not uniformly distributed, so along with the continuous processing, the bottom surface bending or the bottom roughness is not uniform
Solution:
Increase the pulse interval, set the constant pressure of the jet, increasing the gap between the poles, check chip removal frequently.